CN115579847A - Direct current system leakage protection device and protection method - Google Patents
Direct current system leakage protection device and protection method Download PDFInfo
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- CN115579847A CN115579847A CN202211198542.5A CN202211198542A CN115579847A CN 115579847 A CN115579847 A CN 115579847A CN 202211198542 A CN202211198542 A CN 202211198542A CN 115579847 A CN115579847 A CN 115579847A
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- direct current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
Abstract
The invention discloses a direct current system leakage protection device and a protection method, the device comprises an insulation monitoring device, an alternating signal generating circuit, a direct current leakage protection executing device and a direct current breaker, the insulation monitoring device and the alternating signal generating circuit are arranged between a positive bus and a negative bus of a direct current system and are grounded, each direct current branch is provided with the direct current leakage protection executing device and the direct current breaker, when the insulation detecting device detects that the insulation of a specific bus is reduced, the insulation detecting device quits the operation and is put into an alternating signal generating circuit, alternating or pulsating signals are injected into the bus with the reduced insulation, when the direct current branch where the direct current leakage protection executing device is located generates a grounding point, the alternating or pulsating signals form a loop with the alternating current leakage signal generating circuit through the grounding point, and the direct current leakage protection executing device drives the direct current breaker to trip after collecting the alternating or pulsating signals. The invention integrates the leakage detection and the protection into a whole, and reduces the complexity and the cost of system configuration.
Description
Technical Field
The invention relates to a direct current system protection technology, in particular to a direct current system leakage protection device and a direct current system leakage protection method.
Background
The application of the dc system is increasingly widespread, but in the application process, a more economic and efficient technical scheme still needs to be developed for insulation monitoring and leakage current protection of the dc system.
Taking insulation decline location and leakage current protection as an example, the traditional scheme detects the location through insulating detection device cooperation leakage current sensor: the insulation detection device firstly judges that insulation is reduced, and then acquires an unbalanced current signal of a leakage current sensor of a fault branch to realize fault location; however, the leakage current sensor has the problems of high price, incapability of executing protection action and the like; the conventional ac leakage protection device cannot be directly applied to the dc system, and thus a leakage protection method and a corresponding leakage protection executing device suitable for the dc system are needed.
Disclosure of Invention
The invention aims to: the invention aims to provide a leakage protection device for a direct current system, which is used for detecting and protecting the insulation reduction or leakage current fault of a low-voltage direct current system including an IT system.
Another object of the present invention is to provide a method for dc system leakage protection.
The technical scheme is as follows: the invention relates to a direct current system electric leakage protection device, which comprises an insulation monitoring device, an alternating signal generating circuit, a direct current electric leakage protection execution device and a direct current circuit breaker, wherein the insulation monitoring device and the alternating signal generating circuit are arranged between a positive bus and a negative bus of a direct current system and are grounded, each direct current branch is provided with the direct current electric leakage protection execution device and the direct current circuit breaker, when the insulation detection device detects that the insulation of the positive bus or the negative bus is reduced, the insulation detection device is withdrawn from operation and the alternating signal generating circuit is put into use, the alternating signal generating circuit injects alternating or pulsating signals into the bus with the reduced insulation, when a direct current branch where the direct current electric leakage protection execution device is arranged generates a grounding point, the alternating or pulsating signals and the alternating signal generating circuit form a loop through the grounding point, and the direct current electric leakage protection execution device drives the direct current circuit breaker to trip after collecting the alternating or pulsating signals.
Preferably, the dc leakage protection executing device includes a controller, a zero sequence current transformer ZCT, a trip coil L, an adjustable resistor R, a thyristor Q, and a resistor R L The primary coil N1 of the zero sequence current transformer ZCT is connected with a direct current positive bus and a direct current negative bus, the secondary coil N2 is connected with a controller, and one end of a tripping coil L passes through a thyristor Q and a resistor R L The adjustable resistor R is used for adjusting the potential of the trip coil L; the thyristor control electrode is connected with the controller; after the zero sequence current transformer ZCT collects the alternating signals of the direct current branch, the secondary coil N2 generates induced electromotive force to drive the direct current breaker on the direct current branch to trip.
Preferably, the dc leakage protection execution device further includes a test circuit, the test circuit includes a test coil N0, a test button K0 and a piezoresistor R0, the test coil N0 is wound around the iron core of the zero sequence current transformer ZCT, and both ends of the test coil N0 are connected to the positive electrode and the negative electrode of the dc branch circuit through the piezoresistor R0 and the test button K0, respectively.
Preferably, the alternating signal generating circuit comprises an amplifier, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first voltage regulator tube D1 and a second voltage regulator tube D2, wherein the first resistor R1 is parallel to the first capacitor C1, one end of the first resistor R1 is grounded, the other end of the first resistor R1 is connected with the positive input end of the amplifier, one end of the second capacitor C2 is connected with the positive electrode of the amplifier, the other end of the second capacitor C2 is connected with the output end of the amplifier after being connected with the second resistor R2 in series, one end of the third resistor R3 is grounded, the other end of the third resistor R3 is connected with the negative electrode of the amplifier, the first voltage regulator tube D1 and the second voltage regulator tube D2 are connected with the fifth resistor R5 in series after being connected in parallel, and then are connected with the fourth resistor R4 in parallel, and the fourth resistor R4 is connected between the negative electrode and the output end of the amplifier in parallel; the third capacitor C3 is connected in series with the amplifier output and is outside the junction of the fourth resistor R4 and the second resistor R2 with the amplifier output.
Preferably, the protection device further comprises an acoustic and optical signal device, and after the leakage protection execution device collects the alternating signal, the leakage protection execution device outputs a switching value signal through an external circuit to control the acoustic and optical signal device to send out a leakage alarm signal.
The invention relates to a direct current system, which comprises the direct current system leakage protection device.
The invention relates to a leakage protection method of a direct current system, which comprises the following steps:
when the insulation detection device detects that the insulation of the positive bus or the negative bus is reduced, the polarity of the line is judged, the line is stopped from running, the alternating signal generating circuit works, and an alternating or pulsating signal is injected into the line;
when the branch where the direct current leakage protection execution device is located generates a grounding point, the alternating or pulsating signal can form a loop through the grounding point and the alternating signal generation circuit, and the alternating or pulsating signal passes through the direct current leakage protection execution device of the loop;
after the direct current leakage protection execution device detects an alternating or pulsating signal, the direct current breaker of the direct current branch circuit is actuated to cut off a fault branch circuit, or the direct current breaker is tripped through a dry contact or an optical coupler signal sent by the device, or an acoustic and optical signal device is switched on to send out a leakage alarm signal.
Further, the working method of the direct current leakage protection execution device comprises the following steps:
when the system operates normally, no alternating or pulsating signal exists in the zero sequence current transformer ZCT, the sum of current vectors flowing through the positive line and the negative line of the direct current branch is equal to zero, and no corresponding induced electromotive force exists on a secondary coil N2 of the zero sequence current transformer ZCT;
when a direct current branch where the direct current leakage protection execution device is located generates a grounding point, an alternating or pulsating signal can form a loop through the grounding point and an alternating signal generating circuit, and simultaneously the alternating or pulsating signal passes through the direct current leakage protection execution device of the loop and passes through the zero sequence current transformer ZCT, so that the sum of current vectors in the zero sequence current transformer ZCT is not equal to zero, and induced electromotive force is generated on a secondary coil N2;
after the induced electromotive force is processed by the controller, the controller sends out a control signal to enable the thyristor Q to be conducted, the tripping coil L is electrified to enable the direct current breaker P to act, a fault branch circuit is cut off, or an alarm is selected or the direct current breaker is tripped according to a set value, so that direct current leakage protection is realized.
Further, when the test button K0 is pressed, the voltage sensitive resistor R0 is used for simulating DC + leakage, and the voltage sensitive resistor R0 is used for overvoltage protection
When the insulation detection device detects that the insulation of the positive bus or the negative bus is reduced, the insulation detection device is quitted from operation and is put into an alternating signal generating circuit, and the alternating signal generating circuit injects alternating or pulsating signals into the circuit. When a branch where the direct current leakage protection execution device is located generates a grounding point, an alternating or pulsating signal can form a loop with an alternating signal generation circuit through the grounding point, after the zero sequence current transformer ZCT acquires the alternating or pulsating signal, a secondary coil N2 generates induced electromotive force to drive the direct current circuit breaker to trip, a switching value signal can be output through an external circuit (which can be designed according to requirements) according to a detected unbalanced current result, and the signal is used for controlling or switching on switching elements such as the direct current circuit breaker and the like, and an acoustic and optical signal device is connected to send out a leakage alarm signal. The DC leakage protection executing device consists of a trip coil L, a zero sequence current transformer ZCT and a controller part, and is matched with an insulation detection device, an alternating signal generating circuit, a DC circuit breaker and the like for use.
Has the beneficial effects that: compared with the prior art, the invention has the following remarkable technical effects: the direct current leakage protection execution device has the functions of detecting and judging alternating signals, when the insulation detection device detects that leakage or insulation damage occurs in a branch, the insulation detection device is withdrawn from operation and put into an alternating signal generator, the alternating signals and an insulation descending branch form a loop, a zero sequence current transformer in the direct current leakage protection execution device detects unbalanced current and drives a direct current breaker to act and trip, a switching value signal can also be output according to a judgment result, and the signal is used for controlling or switching on switching elements such as the direct current breaker and the like or an acoustic and optical signal device to send a leakage alarm signal; the direct current leakage protection execution device adopts a zero sequence current transformer to replace a leakage current sensor in the configuration process, so that the complexity and the cost of system configuration are reduced while the defect that the leakage current sensor can only detect and can not execute protection actions is overcome; the invention is used for realizing the detection and the protection of the insulation reduction or the leakage current fault of the low-voltage direct current system including the IT system. .
Drawings
FIG. 1 is a diagram of the overall architecture of a DC system;
FIG. 2 is a leakage protection flow chart;
FIG. 3 is a schematic diagram of an earth leakage protection actuator;
fig. 4 is a circuit diagram of an alternating signal generator.
Detailed Description
As shown in fig. 1, an electric leakage protection method for a dc system combines an insulation detection device, an alternating signal generation circuit, a dc circuit breaker, and a dc electric leakage protection execution device. The insulation detection device and the alternating signal generating circuit can be independent circuit units or can be integrated into a whole; the direct current leakage protection execution device has the functions of detecting and judging alternating or pulsating signals, when the insulation detection device detects that the insulation of the bus is reduced, the leakage or insulation damage in the bus or the branch can be judged, at the moment, the insulation detection device quits operation and is put into an alternating signal generating circuit, the alternating signal generating circuit and the insulation reduction branch form a loop, a zero sequence current transformer in the direct current leakage protection execution device detects unbalanced current to drive a direct current breaker to operate and trip, a switching value signal can be output through an external circuit (which can be designed according to requirements) according to the detected unbalanced current result, and the signal is used for controlling or switching on switching elements such as the direct current breaker and the like or switching on an acoustic and optical signal device to send a leakage alarm signal.
As shown in fig. 2, when the insulation is lowered, the dc system works as follows:
(1) When the insulation detection device detects that the insulation of the positive bus or the negative bus is reduced, the polarity of the line is judged and the line stops running, the alternating signal generating circuit works, and an alternating or pulsating signal is injected into the bus;
(2) When the branch where the direct current leakage protection execution device is located generates a grounding point, the alternating or pulsating signal can form a loop through the grounding point and the alternating signal generation circuit, and meanwhile, the alternating or pulsating signal passes through the direct current leakage protection execution device of the loop;
(3) After the direct current leakage protection executing device detects the alternating or pulsating signal, the direct current breaker is actuated to cut off the fault branch, or the direct current breaker can be tripped through a dry contact or an optical coupler signal sent by the direct current leakage protection executing device, or an acoustic and optical signal device is switched on to send out a leakage alarm signal.
As shown in fig. 3, which is a schematic diagram of a dc leakage protection executing apparatus, the dc leakage protection executing apparatus includes a controller, a zero sequence current transformer ZCT, a trip coil L, an adjustable resistor R, a thyristor Q, and a resistor R L The primary coil N1 of the zero sequence current transformer ZCT is connected with a direct current bus, the secondary coil N2 is connected with a controller, and one end of a trip coil L passes through a thyristor Q and a resistor R L The adjustable resistor R is connected with the positive pole and the negative pole of the direct current branch respectively, and the adjustable resistor R is used for adjusting the potential of the tripping coil L; the thyristor control electrode is connected with the controller; after the zero sequence current transformer ZCT acquires the alternating signal of the direct current branch, the secondary coil N2 generates induced electromotive force to drive the direct current breaker on the direct current branch to trip.
The positive and negative lines (DC +, DC-) of the protected direct current branch pass through the annular iron core of the zero sequence current transformer ZCT to form a primary coil N1 of the transformer, and a winding wound on the annular iron core forms a secondary coil N2 of the zero sequence current transformer ZCT. N0 is the test coil, forms test circuit with test button K0 and piezo-resistor R0, presses test button K0 and can form artificial positive and negative current unbalance to the simulation direct current electric leakage, piezo-resistor R0 plays overvoltage protection.
The working process of the direct current leakage protection execution device is as follows:
(1) When the system operates normally, no alternating or pulsating signal exists in the zero sequence current transformer ZCT, and if no electric leakage occurs, the sum of current vectors flowing through the positive line and the negative line of the direct current branch is equal to zero, so that corresponding induced electromotive force cannot be generated on the secondary coil N2;
(2) When a branch where the direct current leakage protection execution device is located generates a grounding point, an alternating or pulsating signal can form a loop through the grounding point and an alternating signal generation circuit, and meanwhile, the alternating or pulsating signal passes through the direct current leakage protection execution device of the loop and a zero sequence current transformer ZCT, so that the sum of current vectors in the zero sequence current transformer ZCT is not equal to zero, and induced electromotive force is generated on a secondary coil N2;
(3) After the induced electromotive force is processed by the controller, the controller sends out a control signal to enable the thyristor Q to be conducted, the tripping coil L is electrified to enable the direct-current breaker P to act and cut off a fault branch, or an alarm circuit is designed, when the induced electromotive force of the coil N2 reaches an alarm constant value, an alarm is realized, and the purpose of direct-current leakage protection is achieved;
(5) K0 is a test button, and when K0 is pressed down, DC + leakage can be simulated, so that the test purpose is achieved; r0 is a piezoresistor and plays a role in overvoltage protection.
Fig. 4 is a schematic circuit diagram of an alternating signal generator, which is a typical venturi bridge circuit, and the alternating signal generator includes an amplifier, a first resistor R1, a second-stage resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first voltage regulator tube D1, and a second voltage regulator tube D2, wherein the first resistor R1 is parallel to the first capacitor C1, and one end of the first resistor R1 is grounded, and the other end of the first resistor R1 is connected to the positive input end of the amplifier, one end of the second capacitor C2 is connected to the positive electrode of the amplifier, the other end of the second capacitor C2 is connected to the output end of the amplifier after being connected to the second resistor R2 in series, one end of the third resistor R3 is grounded, and the other end of the third resistor R3 is connected to the negative electrode of the amplifier, the first voltage regulator tube D1 and the second voltage regulator tube D2 are connected to the fifth resistor R5 in series after being connected to the amplifier in parallel, and then connected to the fourth resistor R4 in parallel, and the fourth resistor R4 is connected between the negative electrode and the output end of the amplifier in parallel; the third capacitor C3 is connected in series at the output of the amplifier and outside the junction of the fourth resistor R4 and the second resistor R2 with the output of the amplifier.
The output frequency can be controlled by arranging the values of the first resistor R1, the second resistor R2, the first capacitor C1 and the second capacitor C2, and taking R1= R2, C1= C2, frequency f = 1/(2 × pi R × C), and the third capacitor C3 as a dc blocking capacitor. The third resistor R3, the fourth resistor R4 and the fifth resistor R5 control the amplification factor, the initial amplification factor A =1+ R4/R3, and the first voltage-regulator tube D1 and the second voltage-regulator tube D2 form an amplitude stabilizing circuit, and the first voltage-regulator tube D1 and the second voltage-regulator tube D2 are not conducted because the input-output voltage difference of the amplification circuit is small at the beginning; when the input-output difference value is increased, the first voltage-regulator tube D1 and the second voltage-regulator tube D2 are conducted, and the fifth resistor R5 and the fourth resistor R4 are connected in parallel, so that the resistance value is reduced, the oscillation amplitude is weakened, and the effect of amplitude stabilization is achieved. And an alternating signal generating circuit can be designed by adopting a timer, a singlechip and the like to realize alternating signal output.
Claims (9)
1. A direct current system leakage protection device is characterized by comprising an insulation monitoring device, an alternating signal generating circuit, a direct current leakage protection executing device and a direct current breaker, wherein the insulation monitoring device and the alternating signal generating circuit are arranged between a positive bus and a negative bus of a direct current system and are grounded, the direct current leakage protection executing device and the direct current breaker are arranged on each direct current branch, when the insulation detecting device detects that the positive bus or the negative bus is lowered in insulation, the insulation detecting device quits operation and is put into the alternating signal generating circuit, the alternating signal generating circuit injects alternating or pulsating signals into the bus which is lowered in insulation, when the direct current branch where the direct current leakage protection executing device is located generates a grounding point, the alternating or pulsating signals can form a loop with the alternating signal generating circuit through the grounding point, and the direct current leakage protection executing device drives the direct current breaker to trip after collecting the alternating or pulsating signals.
2. A leakage protection device for dc system according to claim 1, wherein the dc leakage protection performing device comprises a controller, a zero sequence current transformer ZCT, a trip coil L, an adjustable resistor R, a thyristor Q and a resistor R L The primary coil N1 of the zero sequence current transformer ZCT is connected with a direct current positive bus and a direct current negative bus, the secondary coil N2 is connected with a controller, and one end of a tripping coil L passes through a thyristor Q and a resistor R L The adjustable resistor R is connected with the positive pole and the negative pole of the direct current branch respectively, and the adjustable resistor R is used for adjusting the potential of the tripping coil L; the thyristor control electrode is connected with the controller; after the zero sequence current transformer ZCT collects the alternating signals of the direct current branch, the secondary coil N2 generates induced electromotive force to drive the direct current breaker on the direct current branch to trip.
3. The leakage protection device of claim 2, wherein the dc leakage protection performing device further comprises a testing circuit, the testing circuit comprises a testing coil N0, a testing button K0 and a voltage dependent resistor R0, the testing coil N0 is wound around the iron core of the zero sequence current transformer ZCT, and two ends of the testing coil N0 are respectively connected to the positive pole and the negative pole of the dc branch through the voltage dependent resistor R0 and the testing button K0.
4. The leakage protection device of a direct current system according to claim 1, wherein the alternating signal generating circuit comprises an amplifier, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first voltage regulator tube D1 and a second voltage regulator tube D2, wherein the first resistor R1 is parallel to the first capacitor C1, one end of the first resistor R1 is grounded, the other end of the first resistor R1 is connected to the positive input end of the amplifier, one end of the second capacitor C2 is connected to the positive electrode of the amplifier, the other end of the second resistor R2 is connected to the output end of the amplifier in series, one end of the third resistor R3 is grounded, the other end of the third resistor R3 is connected to the negative electrode of the amplifier, the first voltage regulator tube D1 and the second voltage regulator tube D2 are connected to the fifth resistor R5 in series after being connected to the amplifier in parallel, and then connected to the fourth resistor R4 in parallel, and connected between the negative electrode of the amplifier and the output end; the third capacitor C3 is connected in series with the amplifier output and is outside the junction of the fourth resistor R4 and the second resistor R2 with the amplifier output.
5. The leakage protection device of claim 1, further comprising an audio/optical signal device, wherein the leakage protection executing device outputs a switching value signal through an external circuit after collecting the alternating signal, and controls the audio/optical signal device to send out a leakage alarm signal.
6. A dc system characterized in that it comprises a dc system earth leakage protection device according to any of claims 1-5.
7. A leakage protection method for a direct current system is characterized by comprising the following steps:
when the insulation detection device detects that the insulation of the positive bus or the negative bus is reduced, the polarity of the line is judged and the line is stopped from running, the alternating signal generating circuit works, and an alternating or pulsating signal is injected into the line;
when the branch where the direct current leakage protection execution device is located generates a grounding point, the alternating or pulsating signal can form a loop through the grounding point and the alternating signal generation circuit, and the alternating or pulsating signal passes through the direct current leakage protection execution device of the loop;
after the direct current leakage protection execution device detects an alternating or pulsating signal, the direct current breaker of the direct current branch circuit is actuated to cut off a fault branch circuit, or the direct current breaker is tripped through a dry contact or an optical coupler signal sent by the device, or an acoustic and optical signal device is switched on to send out a leakage alarm signal.
8. The leakage protection method of the dc system according to claim 7, wherein the dc leakage protection performing device operates by:
when the system operates normally, no alternating or pulsating signal exists in the zero sequence current transformer ZCT, the sum of current vectors flowing through the positive line and the negative line of the direct current branch is equal to zero, and no corresponding induced electromotive force exists on a secondary coil N2 of the zero sequence current transformer ZCT;
when a direct current branch where the direct current leakage protection execution device is located generates a grounding point, an alternating or pulsating signal can form a loop through the grounding point and an alternating signal generating circuit, and simultaneously the alternating or pulsating signal passes through the direct current leakage protection execution device of the loop and passes through the zero sequence current transformer ZCT, so that the sum of current vectors in the zero sequence current transformer ZCT is not equal to zero, and induced electromotive force is generated on a secondary coil N2;
after the induced electromotive force is processed by the controller, the controller sends out a control signal to enable the thyristor Q to be conducted, the trip coil L is electrified to enable the direct current breaker P to act, a fault branch is cut off, or an alarm is selected or the direct current breaker is tripped according to a set value, so that direct current leakage protection is realized.
9. A leakage protection method for DC systems according to claim 8, characterized in that when the test button K0 is pressed, it is used to simulate DC + leakage, and the voltage dependent resistor R0 is used for overvoltage protection.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202211198542.5A CN115579847A (en) | 2022-09-29 | 2022-09-29 | Direct current system leakage protection device and protection method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211198542.5A CN115579847A (en) | 2022-09-29 | 2022-09-29 | Direct current system leakage protection device and protection method |
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| CN115579847A true CN115579847A (en) | 2023-01-06 |
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| CN202211198542.5A Pending CN115579847A (en) | 2022-09-29 | 2022-09-29 | Direct current system leakage protection device and protection method |
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